from math import *

x1, y1, x2, y2 = map(float, raw_input().split())
distance = sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2))
print distance from math import * x1, y1, x2, y2 = map(float, raw_input().split()) x1 map(float, raw_input().split()) map float raw_input().split() ().split () raw_input split y1 x2 y2 distance = sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2)) distance sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2)) sqrt (x1-x2)*(x1-x2) + (y1-y2)*(y1-y2) (x1-x2)*(x1-x2) x1-x2 x1 x2 x1-x2 x1 x2 (y1-y2)*(y1-y2) y1-y2 y1 y2 y1-y2 y1 y2 print x1, y1, x2, y2 = map(float, raw_input().split()) map(float, raw_input().split()) x1 distance = sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2)) sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2)) distance y1, x2, y2 = map(float, raw_input().split()) map(float, raw_input().split()) y1 x2, y2 = map(float, raw_input().split()) map(float, raw_input().split()) x2 y2 = map(float, raw_input().split()) map(float, raw_input().split()) y2
from math import *

x1, y1, x2, y2 = map(float, raw_input().split())
distance = sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2))
print distance